The present invention relates generally to methods for modifying weld control parameters in an automated welding process based on measurements of a weld bead features and measurements of a weld seam taken before the weld bead is applied.
A welding process is used to join one metal work piece to a second metal work piece by bringing abutting surfaces from the two work pieces into a molten state. A welded joint is subjected to high stresses resulting from high application loads and residual stresses that pre-exist in the joint due to localized heating and cooling cycles that occur during the welding process. The quality of a welded joint directly relates to the fatigue resistance of the joint as it experiences these high stresses.
Typically, a weld bead is applied along the abutting surfaces of the work pieces during the welding process. The abutting surfaces form a weld seam or weld joint between the work pieces. This weld bead is received within the seam and extends along the length of seam as directed by a controller used in an automated welding process. If the geometry of the weld bead is poor, the life of the welded joint will be short. For example, if the weld includes a sharp notch between the weld bead and the work piece, the joint will usually have a short fatigue life. When using an automated welding process it is important to monitor characteristics of the weld bead to ensure that the weld bead is within a predetermined range of parameters. One important weld bead characteristic to monitor is the weld toe radius, which is formed at the interface between the weld bead and the work piece. If a certain weld bead characteristic is not within an acceptable parameter range, corrections need to be made to the welding process to ensure the quality of the weld bead. It is also important to monitor characteristics of the weld seam to anticipate any seam irregularities that could possibly affect the quality of the weld bead. If seam irregularities are detected, corrections can be made to the welding process to improve the quality of the weld bead as it is applied. Thus, it is important to have a method for modifying welding control parameters in an automated welding apparatus by monitoring the weld seam and the weld bead to continuously provide the highest quality weld bead and for ensuring high fatigue resistance.
The present invention is directed to a system for controlling the quality of a weld during a weld process comprising of a first work piece and a second work piece supported relative to said first work piece to define a weld seam therebetween. In addition, there is a first sensor for measuring weld seam characteristics to produce a weld seam signal representing a weld seam profile and an automated welding apparatus for applying a weld bead along said weld seam to join said first work piece to said second work piece and a second sensor for measuring weld bead characteristics to produce a weld bead signal representing an actual weld bead profile and a controller for comparing said weld seam signal to said weld bead signal and modifying the weld process if there is a difference between the weld seam signal and the weld bead signal.
In one aspect of this invention, a method for controlling the quality of a weld during a weld process where the weld process includes an automated welding apparatus for applying a weld bead along a weld seam to join a first work piece to a second work piece, includes the steps of: measuring weld seam characteristics to obtain a first set of data; determining a weld seam profile based on the first set of data; predicting a desired weld bead profile based on the weld seam profile; determining optimal welding parameters for the weld process to achieve the desired weld bead profile; applying the weld bead along the weld seam; measuring weld bead characteristics to obtain a second set of data for defining an actual weld bead profile; comparing the desired weld bead profile to the actual weld bead profile; and modifying the weld process if there is a difference between the actual weld bead profile and the desired weld bead profile.
In another aspect of this invention, a method for controlling the quality of a weld during a weld process where the weld process includes an automated welding apparatus with a feed-forward controller and a feedback controller for applying a weld bead along a weld joint, includes the steps of: measuring weld joint characteristics to obtain a first set of data; determining a weld joint profile based on the first set of data; predicting optimal welding parameters for the weld process to achieve an optimal weld bead profile based on the weld joint profile; generating a feed-forward prediction signal representing the optimal welding parameters; applying the weld bead along the weld joint; measuring weld bead characteristics to obtain a second set of data for defining an actual weld bead profile; generating a feedback measurement signal representing the actual weld bead profile; comparing the feedback measurement signal to the feed-forward prediction signal; and modifying the weld process in real time if there is a difference between the feed-forward prediction signal and the feedback measurement signal.
In still another aspect of this invention, a system for controlling the quality of a weld during a weld process includes a first work piece and a second work piece supported relative to said first work piece to define a weld seam therebetween. In addition, there is a first sensor for measuring weld seam characteristics to produce a weld seam signal representing a weld seam profile and an automated welding apparatus for applying a weld bead along said weld seam to join said first work piece to said second work piece and a second sensor for measuring weld bead characteristics to produce a weld bead signal representing an actual weld bead profile. In addition, there is a controller for comparing said weld seam signal to said weld bead signal and modifying the weld process if there is a difference between the weld seam signal and the weld bead signal.